Method of waxing paper and paper board and apparatus



1964 R. P. MAHONEY 3,145,1 18

METHOD OF WAXING PAPER AND PAPER BOARD AND APPARATUS Filed Sept. 13.1960 IN VEN TOR. @4144 15/724 0/1 [2 444 ATT QNEYS United States Patent3,145,118 METHUD 0F WAXlf -IE PAPER AND PAPER IBQARD AND APPARATUS Ralphll. Mahoney, Beloit, Wis assignor to lieluit Iron Works, lileloit, Win,a corporation of Wisconsin Filed Sept. 133, 196th, Ser. No. 55,755 4Claims. (Cl. 117--65.2)

The present invention relates broadly to the production of paper andrelated web materials, and is more particularly concerned with improvedmethods and means for waxing and finishing paper and related webmaterials.

Heretofore, waxes have been applied to paper and paper products invarious blends and of various compositions for the purpose of primarilyexcluding moisture but also to enhance appearance and to provide adegree of self-sealing. Tissue and lightweight papers are waxed for foodservice to prevent such food products as meat, cheese, bread and thelike from sticking to the paper. The Wax employed for this purpose isusually dry wax and the wax is applied to the fibers of the paper webrather than to the surface thereof. This waxed product carries thesmallest quantity of wax relative to the weight of the paper. Householdwaxed papers and bread-wrap are required to have an unbroken film of waxfor preventing penetration of moisture and vapors. It is also desirableto provide a high gloss finish to such waxed papers. Recently, paperboard for the food industry is primarily surfaced with a wax moisturebarrier.

For purposes of the present application, the term wax is to beunderstood as designating paraffin, emulsions of parafiin, and anymixture of parafiin and solvent, and similar wax materials employed forwaxing of paper and related Web materials.

The present invention permits greater production speeds, requires theuse of less wax to obtain a continuous waxed surface, permits uniformapplication of the wax to the web surface, and provides improvedappearance to the waxed web surface.

It is therefore an object of the present invention to finish a Waxedsurface of a paper web and related web materials.

It is another object of the present invention to provide improvedmethods and means for imparting a high gloss finish to a waxed surfaceof a paper web and related web materials.

It is still another object of the present invention to provide improvedmethods and means for impregnating Wax into the surface of a paper weband related web material by the application of controlled amounts ofheat and pressure while simultaneously imparting a finish to the waxedsurface.

It is a further object of the present invention to provide improvedmethods and means for applying a uniform layer of wax to at least onesurface of a paper web and related web material and for imparting afinish to the layer.

A still further object of the present invention is to provide improvedmethods and means for waxing one or both sides of a paper web andrelated web material and for finishing one or both sides of waxedsurfaces of the paper web or related web material.

Other objects, features and advantages will become apparent from aconsideration of the following detailed description and accompanyingdrawing illustrating preferred embodiments of the present inventionwherein like reference numerals and characters refer to like andcorresponding parts throughout the several views.

On the drawing:

FIGURE 1 is a partially diagrammatic view in side elevation of apparatusfor waxing and finishing surfaces of paper web and related web materialsconstructed in accordance with the concepts of the present invention.

FIGURE 2 is a diagrammatic view in side elevation of apparatus forwaxing and finishing both sides of a web material.

As shown on the drawing:

Briefly stated, the present invention involves the application of a filmof Wax to a hard, hot polished surface, pressing the Web material firmlyagainst the hot polished surface and removing the web material fromcontact with the solid surface while simultaneously releasing thepressure applied thereagainst.

As appears in FIGURE 1, apparatus constructed in accordance with thepresent invention for waxing and finishing one side of a paper web orpaper board may include a wax supply conduit 3 for delivering Wax to aconventional flexible blade applicator 4 confining a puddle of the wax Sin contact with a driven roll 6 having a highly polished finishingsurface 7. The finishing roll 6 is heated to provide a heated surface,and for this purpose, a heating medium may be supplied to the interiorof the roll 6 through a conduit 8. It will be appreciated that the sizeof the finishing roll 6 is much smaller relative to the size of a Yankeedrum.

A web W is fed by conventional means (not shown) through a narrow widthand hard nip N defined by the finishing roll 6 and a hard surface butresilient backing roll 9.

The finishing roll 6 may have a surface plating, as with chrome ornickel, and the resilient backing roll 9 may comprise a metal corehaving a rubber cover of the desired hardness.

In order to minimize the operating pressure loading of the respectivefinishing and backing roll, it is desirable that the resilient roll 9 bequite hard, i.e.., less than 30 P. and J. (MW ball). Employment of ahard surface roll permits concentration of total uniform pressureloading on a relatively narrow nip, in the direction of travel of theweb, and, excellent results have been obtained when the nip is of across-sectional Width less than 1" and preferably about /2. Thedevelopment of high unit pressures in a narrow nip is desirable onlybelow the crushing point of the web fibers. The hard and narrow nipassures uniform loading across the entire width of the sheet. It will beappreciated, of course, that continued use of the nip will tend to causethe resilient or hard rubber surfaced roll 9 to soften slightly due tothe temperature conditions existing at the nip and due to the effects ofworking engagement with the Web during operation. In order to maintainthe backing roll at a desired high hardness level and thereby the nipwidth within the desired limits, means may be employed, if desired tocool the resilient rolls. For this purpose, a cooling agent may beintroduced into the interior of the backing roll through a conduit ha.

The temperatures maintained at the nip in conjunction with the other nipconditions must be controlled to prevent evaporation of the waxesemployed. The temperature limits of the waxes presently employed forpapermaking purposes are well known in the art. Generally, thetemperature at the nip is maintained above the boiling point of water orother vehicle of the web and no known upper temperature limits existother than the decomposition temperatures of the particular wax, sizeand web materials involved. Experience has indicated that thetransversely and uniformly distributed high intensity unit pressure atthe nip is preferably within the range from about 240-25() lbs. per sq.in. to about 2400 lbs. per sq. in., depending primarily upon theparticular wax and paper web material involved.

Thus in the nip, the surface of the paper board to be waxed is pressedfirmly against the finishing surface '7 carrying the waxed film by meansof the backing roll 9. It will be appreciated that the Waxing andfinishing steps occur almost simultaneously in the nip. The temperatureand pressure conditions in the nip result in a smooth and evenapplication of wax which forms thereby a continuous wax film on thesurface of the web. Additionally, the weight distribution of the Wax iseven, and less wax is required to obtain a continuous film for sealingthe wax and/ or obtaining the level of finish desired. It is oftendesirable, particularly to achieve heavier applications of Wax, to applysufiicient wax to the surface 7 to form a small pool of liquid wax atthe entrance to the nip N. It will also be appreciated that the presentinvention is distinguishable from the calendering apparatuses employinghigh unit pressures which tend to press the web and require extendedcontact of the web with the rolls.

Satisfactory finished results are obtained at any practical operatingspeed and, therefore, finishing operation speeds are limited only by theoperational speeds of the paper machine itself or the web supply meansand of the finishing and backing roll. It will also be appreciated thatfinishing temperatures are generally in direct relation to operatingspeeds. For example, satisfactory finishing of waxed board in the abovemanner which was supplied at the rate of 500 ft. per minute was obtainedwith finishing roll and nip temperatures of approximately 300 F. and nippressures of 400 lbs. per linear inch. Similarly, satisfactory finishingresults were obtained with a waxed lightweight paper running at 2000 ft.per minute through a pressure nip of approximately /2" width maintainedat a temperature of 350 F. and pressures between 409 and 500 lbs. persquare inch.

The waxed and finished web may be immediately removed from the nip andfed to a winding reel (not shown).

O-n lightweight pro-waxing stock, the present invention permitssufiicient control of Weight so that the dry waxed grade of paper may beproduced while an improved appearance attributable to a brighter andglossier finish is provided. It is also possible to drive sufiicient waxinto the sheet to provide a waxed paper product having two waxedsurfaces. Of course the waxing of both sides of a paper web in thismanner depends upon the thickness of the paper web being treated.

To vary the pressure applied at the nip for finishing of parti gularwaxed surfaces, means therefore may take the form of a hydraulically orpneumatically operated piston assembly having its piston rod 11connected to a cross arm 12 of a pair of support members 13 which carrybrackets 14 for mounting the shaft 15 of the backing roll 9. The supportmembers 13 may be pivotally mounted to the support stanchion 13.Pneumatic or hydraulic operating pressures of the piston arrangementneed only be increased or decreased in order to produce a correspondingpressure on the finishing roll and web.

Thus, in operation, the web is introduced into the nip N, preferably insuch a manner that the web first contacts the backing roll and wax in acontinuous film is applied to the surface of the web in contact with thefinishing roll 6. The thickness of the wax is easily controlled by thewaxing apparatus 4 as well as the cross-sectional width of the film ofwax to be applied to the web. In the nip, the heat and pressureconditions established therein cooperate to assure the application of acontinuous wax film on the web surface in contact with the finishingroll and to simultaneously finish the surface of the web in contact withthe finishing roll. The now waxed web material is removed from the nipsimultaneously with the release of pressure by the backing roll and maybe thereafter wound on a reeler (not shown). The web upon leaving thenip has a dry waxed surface exhibiting a high finish or gloss. Byregulating the pressure applied by the backing roll 9 the wax may beapplied to the web in the nip in such a manner that the wax penetratesand impregnates the web, depending upon web thickness, so that bothsides of the web are provided with a Waxed surface.

The method and apparatus in the present invention are elficient andprovide neat and clean operating conditions as contrasted with the usualgloss waxing arrangements or water waxing arrangements. The quantity ofwax applied to the Web per unit area may be completely and accuratelycontrolled by the nip loading conditions imposed. As aforementioned,there are many different grades of waxes employed for papermakingpurposes as well as many different grades of paper and board to produceas many different grades and qualities of waxed paper product and boardproduct as is commercially desirable. Thus, temperature, pressure, speedand similar operating conditions will vary depending upon the particularresults desired. Furthermore, the apparatus of the present invention isso compact and simple and the adjustments required toproduce varyinggrades of waxed paper and board so simple and so completely under thecontrol of the apparatus operator that but a brief period ofexperimentation is all that is required to permit thoseskilled in theart to employ the method and apparatus of the present invention toproduce the best results and obtain the desired waxed paper or boardproduct.

Because, unexpectedly, the wax immediately solidifies and has providedthereon a finish when it leaves the nip, a similar waxing and finishingapparatus may be located immediately adjacent the first finishingarrangement for waxing and finishing the other side of the web material.For this purpose, the second finishing roll and second backing roll arereversed as shown in FIGURE 2. In this arrangement the apparatus ofFIGURE 1 is employed in conjunction with a second waxing and finishingapparatus, generally indicated by the numeral 34?, which includes afinishing roll 31 similar in construction and operation to finishingroll 6 mounted on frame stanchion 1301. A hard surface but resilientbacking roll 32, mounted on frame stanchion 18b and similar inconstruction and operation to backing roll 9, cooperates with thefinishing roll 31 under the nip and pressure conditions similar to thoseoutlined herein in connection with the operation of the first waxing andfinishing arrangement to define a finishing nip N, preferably of thesame cross-sectional width as the finishing nip N. With this arrangement36, the opposite side of the web may be waxed and finished in the samemanner and under the same conditions as the web finishing treatmentoccuring in the nip N. The finishing of the second side of the waxed webdoes not materially reduce the finish on the previously finished surfaceof the web nor are the other'desirable characteristics of the webmaterially affected while finishing the second side of the web. Means 33for varying the pressure loading on the web in the nip, similar inconstruction and operation to the hydraulically or pneumaticallyoperated piston assembly 14) may be provided and mounted on a framecross arm 18c.

Preferably the paper web or board is brought in contact with the backingroll for positioning of the web for delivery to the nip. The web in thenip is provided with a continuous waxed film and the conditions at thenip including the heat and pressure applied, are sufficient to provide agloss finish to the waxed surface. The web remains in the nip but ashort time depending upon the operational speed of the web supply means.Upon leaving the hard and narrow width nip N the newly waxed andfinished surface of the web immediately sets and may be then wound on areeler (not shown).

Waxed paper finished in accordance with the present invention produces afinish comparable to commercial finishes for waxed paper now consideredacceptable in the trade. Satisfactory finishing results have beenobtained for various waxed papers and board with the finishing surfaceof the finishing roll heated to a temperature within the range fromabout 220 F. to about 400 F., while I prefer to employ temperatureswithin the range from about 280 F. to 360 F. depending upon the endproduct desired.

111 general the heat and pressure in the hard, narrow nip should becontrolled to conform the surface being finished to the surface of thefinishing roll without crushing the web and under conditions whichaccommodate removal of the web without disturbing the conformed websurface, Usually, tolerable moisture contents are lessened withincreases in either nip temperature or nip pressure and enlarged withincreases in basis web weight.

Conventional calenderlng operations, it will be appreciated, whereinhigh pressures are applied to the Web, have an effect on web density andthickness which differs from the effects of the nip conditions of thepresent invention which permit lower pressures to be applied to the webin the hard narrow width nip. Lesser web deformation therefore occursand results in a more uniformly finished. Web surface.

Various Waxing apparatus may be employed for applying the Wax to thefinishing roll and the products obtained in accordance with the presentinvention may be employed for a variety of purposes, such as wax paper,frozen food boxes, frozen food Wrap and related applications.

Although various minor modifications might be suggested by those versedin the art, it should be understood that I wish to embody Within thescope of the patent warranted hereon all such embodiments as reasonablyand properly come within the scope of my contribution to the art.

I claim as my invention:

1. The method of wax-finishing surfaces of paper web materials andrelated web materials Which comprises: applying wax to a finishingsurface cooperating with a resiliently yieldable backing surface of ahardness less than 30 P. and I. (%s ball) to define a hard and narrowwidth finishing nip, maintaining the nip at a pressure within the rangeof from about 240-250 p.s.i. and about 2400 p.s.i. and at a temperatureWithin the range from about 200 F. to about 400 F. to thereby finish awaxed surface in the nip, and passing a Web material through the nipwhereby the surface of the web material adjacent the finishing surfaceis waxed and finished in the nip.

2. Apparatus for wax-finishing surfaces of paper Web materials andrelated web materials comprising: a finishing roll, means for applying aWax film to the finishing roll, a resiliently yieldable backing rollhaving a hardness less than 30 P. and J. ball) cooperating with thefinishing roll to define a hard and narrow width nip of across-sectional width less than 1", means for maintaining the nip at atemperature within the range of from about 200 F. to about 400 F, meansfor maintaining the nip at a pressure within the range of from about240-250 p.s.i. to about 2400 p.s.i., whereby a paper web material passedthrough the finishing nip is provided with a waxed surface in the nipwhich is finished in the 111p.

3. Apparatus as claimed in claim 2 wherein the temper-attire maintainingmeans comprises means for supplying heated fluid to the interior of saidfinishing roll.

4. Apparatus as claimed in claim 2 wherein the nip pressure maintainingmeans comprises resilient fluid pressure actuated means.

References Cited in the file of this patent UNITED STATES PATENTS1,385,042 Decker et al. July 19, 1921 1,429,928 Carter Sept. 26, 19221,669,381 Nunez May 8, 1928 1,719,166 Bradner July 2, 1929 2,417,009Miller Mar. 4, 1947 2,554,663 Cowgill May 29, 1951 2,919,205 Hart Dec.29, 1959 3,070,457 Labombarde Dec. 25, 1962

1. THE METHOD OF WAX-FINISHING SURFACES OF PAPER WEB MATERIALS ANDRELATED WEB MATERIALS WHICH COMPRISES: APPLYING WAX TO A FINISHINGSURFACE COOPERATING WITH A RESILIENTLY YIELDABLE BACKING SURFACE OF AHARDNESS LESS THAN 30 P. AND J. (1/8" BALL) TO DEFINE A HARD AND NARROWWIDTH FINISHING NIP, MAINTAINING THE NIP AT A PRESSURE WITHIN THE RANGEOF FROM ABOUT 240-250 P.S.I. AND ABOUT 2400 P.S.I. AND AT A TEMPERATUREWITHIN THE RANGE FROM ABOUT 200*F. TO ABOUT 400*F. TO THEREBY FINISH AWAXED SURFACE IN THE NIP, AND PASSING A WEB MATERIAL THROUGH THE NIPWHEREBY THE SURFACE OF THE WEB MATERIAL ADJACENT THE FINISHING SURFACEIS WAXED AND FINISHED IN THE NIP.